1.A. Field of the Invention
The present invention relates to saws used for cutting circular holes through objects made of wood and various other materials, of the type utilizing a cylindrical -saw cup coaxially fastened to an arbor holding a pilot drill which protrudes forward of cutting teeth provided on a front annular surface of the saw cup. More particularly the invention relates to a hole saw which automatically ejects a plug sawed from a workpiece, in which hole saw cups of various diameters may readily be interchangeably mounted on a novel arbor-holder by a twisting, snapping action.
2. B. Description of Background Art
In U.S. Pat. Nos. 4,741,651 and 5,096,341, the present inventor disclosed plug ejecting hole saws which utilize a left-hand threaded mandrel or arbor that holds a pilot drill, the shank of which is secured in an enlarged diameter flange or collar located at the front end of the arbor. The arbor is screwed into a threaded, arbor-holder bore disposed coaxially through a bushing or thicker portion of a circular disk-shaped base plate which forms the rear end wall of a cup-shaped saw body which has angled circumferentially spaced apart cutting teeth in the front annular end wall thereof. In a hole saw cup of this type, the front, cup-shaped portion of the saw cup and the thicker rear base plate or arbor-holder bushing are generally fabricated as separate metal parts which are brazed together. Thus, this type of hole saw is sometimes referred to as a xe2x80x9cbi-metalxe2x80x9d hole saw.
A novel feature of the inventions disclosed in the aforementioned patents of the present inventor comprises left-hand threading of both the outer surface of the arbor and the inner threaded bore through the saw cup base. With this arrangement, when the arbor is threaded counterclockwise into the saw cup arbor-holder bore, as viewed from the front of the saw cup and pilot drill end of the arbor, the front flange portion of the arbor advances rearwardly to seat against the inner front wall surface of the saw cup base. The arbor shank, which protrudes rearwardly from the saw cup base is then secured in the collet of a power drill. When the power drill is powered on to turn the pilot drill bit and saw in the usual clockwise cutting direction, as viewed from the rear, shank end of the bit, a counterclockwise reaction torque is exerted on the saw cup teeth by frictional resistance offered by workpiece in response to the cutting action, tending to further tighten and secure the arbor flange against the inner surface of the saw cup base. When the saw cup has penetrated the thickness of a workpiece such as a door panel, a cylindrically-shaped plug of workpiece material becomes lodged tightly within the saw cup, and in prior art hole saws, is difficult to remove from the saw cup. However, in accordance with the ""651 and ""341 patents, a plug lodged within the saw cup may readily be ejected by powering the drill in a reverse, i.e., counterclockwise direction after a hole has been bored through a workpiece, while maintaining the saw cup stationary. Rotating the drill shank and arbor in a counterclockwise direction by the power drill causes the arbor to be advanced axially forward within the threaded bore of the saw cup, and the front flange of the arbor to abut the rear surface of the plug and eject it forward out of the saw cup bore.
The above-described plug ejecting feature of hole saws disclosed in the present inventors ""651 and ""341 patents has provided a highly effective and widely accepted improvement in bimetal hole saws. Subsequent to issuance of those two patents, U.S. Pat. No. 5,435,672 was issued for adapters having a left-hand threaded arbor-receiving bore, and a right-hand external bore. The adapters were designed to be threaded into right-hand threaded arbor-holder bores of existing saw cups, thus accommodating left-hand threaded arbors and permitting the present inventor""s novel plug ejecting function to be accomplished using existing hole saw cups having right-hand threaded arbor-holder bores.
Although the novel plug ejecting hole saws disclosed in the present inventor""s ""651 and ""341 patents constituted a substantial advancement in the art for hole saws having a base provided with a threaded bore for receiving an arbor, there is another type of widely employed hole saw cup which heretofore could not utilize the advantageous plug ejecting construction disclosed in those patents. This type of hole saw is sometimes referred to as a xe2x80x9cCarbonxe2x80x9d type, since it uses hole saw cups fabricated as a unitary structure, e.g., a deep drawn cup, made from high carbon steel. In this type of hole saw, the saw cup base is made of relatively thin stock, thus precluding the use of threaded bore through the base as a means for attaching the saw cup to an arbor. Instead, this type of hole saw typically is provided with a non-circular, e.g., a double-D-shaped central bore through the base of the hole saw cup, which receives the complementary-shaped, enlarged rear portion of an arbor which is secured to the base by a threaded fastening member.. The present invention was conceived of to provide a plug ejecting hole saw which may utilize thin base wall, non-threaded saw cups of the type described above.
An object of the present invention is to provide a plug ejecting hole saw including an arbor-holder which can be attached to hole saw cups of various sizes.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder which can be secured to the base of a hole saw cup with non-threaded fastening means.
Another object of the invention is to provide a plug ejecting hole saw including a hole saw cup having a right-hand threaded arbor-securing bore through the base of the hole saw cup, and an arbor-holder or adapter press fittable into the arbor securing bore of the saw cup and having through the adapter a left-hand threaded bore for threadingly receiving an arbor.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder which is removably securable to the base of a non-threaded hole saw cup having an unthreaded aperture through the base of the hole saw cup for attaching to an arbor, the arbor-holder having therethrough an axially disposed left-hand threaded bore for threadingly receiving an arbor.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder which is removably securable in an unthreaded aperture through the base of a hole saw cup, without accessing the interior of the hole saw cup.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder which is removably securable to a hole saw cup provided with a non-circular aperture through its base, the arbor-holder having a front nose piece insertable forward through the aperture, and locking tabs which spring forward to lock the arbor-holder axially with respect to the saw cup when the arbor-holder is rotated with respect to the saw cup base.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder having an outer collar and inner body disposed axially therethrough, the inner body having a lefthand threaded bore disposed axially therethrough for receiving an arbor, a front nose piece slidably holding locking tabs and circumferential grooves which cooperate to lockingly engage the base of a hole saw cup when the front nose piece has been inserted into and rotated in a first direction within an aperture provided through the base of saw cup, the locking tabs and grooves being released from locking engagement with the saw cup base when the collar of the arbor-holder is pulled axially rearward with respect to the inner body thereof and rotated in the opposite direction.
Another object of the invention is to provide a plug ejecting hole saw including an arbor-holder having an outer collar which axially slidably holds an inner body having disposed axially therethrough a left-hand thread for receiving an arbor, the inner body having a first, front, nose piece snapping lockingly engageable and releasable within a first size aperture through a selected one of a first plurality of hole saw cups, and a second, rear, nose piece releasably engageable within a second size aperture through a selected one of a second plurality of hole saw cups.
Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims.
It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, I do not intend that the scope of my exclusive rights and privileges in the invention be limited to details of the embodiments described. I do intend that equivalents, adaptations and modifications of the invention reasonably inferable from the description contained herein be included within the scope of the invention as defined by the appended claims.
Briefly stated, the present invention comprehends a hole saw for use with power drills which automatically ejects a cylindrically-shaped plug produced in cutting a hole through an object by the drill powered in a first direction, when the power drill is operated in the opposite direction.
A plug ejecting hole saw according to the present invention includes an arbor-holder removably attachable to a selected one of a plurality of hole saw cups of various sizes. A main embodiment of a plug ejecting hole saw according to the present invention includes an arbor-holder removably attachable to a selected hole saw cup of the type having a cylindrical cup-shaped body provided with angled cutting teeth protruding from the front annular surface of the body, and a relatively thin rear circular base wall having through its thickness dimension a non-circular aperture for attachment to an arbor concentrically aligned with the front annular surface of the body, A preferred arbor attachment aperture for saw cups according to the present invention has a xe2x80x9cdouble-Dxe2x80x9d shaped perimeter formed from diametrically opposed arc segments of a circle which is concentric with the circular hole saw cup face, the circle being truncated on opposite sides thereof by a pair of chords equidistant from and parallel to a diameter which perpendicularly bisects the arcs. Thus, a preferred arbor attachment aperture provided through the base of a saw cup according to the present invention has an inner peripheral edge wall consisting of a pair of diametrically opposed laterally symmetric circular arc segments centered at 90-degree and 270-degree locations of a circle, and two diametrically opposed flat vertical segments centered on zero-degree and 180-degree locations of the circle. A main embodiment of an arbor-holder for use with hole saw cups of the type having a double D-shaped arbor-holder aperture through the base of the saw cup includes an outer cylindrical housing or collar having therethrough a circular bore which axially slidably holds a body having cylindrical outer wall surfaces which fit within the bore. The cylindrical body has a nose piece or boss which protrudes axially outwardly of the front annular surface of the collar, the nose piece having a longitudinally or axially disposed outer surface with an outer transverse cross-sectional shape similar to that of a double-D-shaped arbor-holder aperture through a saw cup base, but having a slightly smaller size which facilitates insertion of the nose piece into the aperture.
The nose piece has a pair of transversely disposed grooves, each of which extends radially inwardly into a separate one of two axially disposed, curved side walls of the nose piece, each of the grooves having a transverse or outer edge wall located inwardly of and parallel to the outer transverse edge wall or front face of the nose piece. The rear or inner edge wall of each of the two transversely disposed grooves is defined by the front or outer transversely disposed annular wall surface of the cylindrical body within the collar.
Each of the two transverse nose-piece grooves is disposed circumferentially from a location circumferentially spaced apart from a junction between a flat and curved side of the double-D-shaped nose piece. Thus the transverse grooves form a pair of axial shoulder ribs, which are disposed rearwardly or axially inwardly from the front transverse face of the nose piece to the front or outer transverse surface of the cylindrical body. The nose piece also includes a pair of diametrically opposed, rectangularly-shaped longitudinal grooves formed in opposite flat sides of the nose piece, which are disposed rearwardly or axially inwardly from a transverse plane located axially inwardly or rearwardly of the front or outer transverse face of the nose piece, but axially outwards or forward of a transverse plane containing the front or outer transverse edge walls of the transverse grooves.
Each of the two diametrically opposed longitudinal grooves is centered on a longitudinal plane which bisects the two diametrically opposed flats of the nose piece. Also, each longitudinal groove is disposed rearwardly or axially inwardly through an adjacent transverse groove and extends through the inner cylindrical body to a location forward of the rear transverse wall surface of the inner cylindrical body, and penetrates the outer cylindrical wall surface of the inner cylindrical body. Each longitudinal groove longitudinally slidably receives a locking tab support lug having a front locking tab portion which has a length approximating that of that portion of the longitudinal groove located in the nose piece, and a radial thickness slightly greater than that of the radial depth of the groove. Each lug also has a rear portion of greater thickness than the front tab portion, and is slidably received within that portion of a longitudinal groove located within the inner cylindrical body. The rear portion of each lug is urged axially forward by first spring means comprising a compression spring, and is limited in forward axial movement by contact of a retainer pin attached to the lug and slidably received within a threaded blind bore axially disposed within the collar, with an end wall of the bore. The arbor-holder also includes second spring means which resiliently urges the inner cylindrical body of the arbor-holder rearward or axially inwardly within the collar.
When the inner cylindrical body of the arbor-holder is pushed axially forward or outwardly from the collar against the resilient force provided by the first spring means, the nose piece is displaced forward or axially outwardly of the front annular face of the collar. This displacement causes the front shoulder edges of the longitudinal tab grooves to move forward of the front transverse edge walls of the tabs. With the cylindrical inner body pushed sufficiently far forward within the collar, the rear transverse edge walls of the transversely disposed grooves are moved axially outwards or forward of the front edges of the tabs, unblocking the junctions or passageways between each transverse groove and the longitudinal tab groove adjacent to it Also, when the nose piece is inserted forward into the arbor-holder aperture of a hole saw cup, contact of the rear surface of the saw cup with the front surfaces of the tabs pushes each tab rearwardly within its longitudinal groove against a restoring force provided by a compression spring. Rearward motion of the tabs unblocks the transverse grooves, thus allowing portions of the peripheral aperture edge wall be rotatably received within adjacent transverse grooves of the nose piece, and thereby allowing the entire arbor assembly to be rotated clockwise with respect to the hole saw cup. When the rotation angle approximates forty-five degrees, each of the two locking tabs springs axially forward in response to spring forces exerted by the compression springs, into a separate one of the two radial clearance spaces formed between each nose piece flat holding a tab, and an adjacent curved inner peripheral edge wall of the saw cup aperture. In this position, the curved portions of the nose piece, which have outer longitudinal surfaces spaced farther apart than the flats of the peripheral wall adjacent the aperture through the saw cup base, are axially aligned with the peripheral wall flats. Thus, the peripheral wall flats are retained axially within the transverse nose piece grooves in this position. Further clockwise rotation of the arbor-holder with respect to the saw cup base is limited by contact of an axially disposed nose piece rib with an intersection between the curved and flat portions of the peripheral edge wall of the hole saw cup aperture. Counterclockwise rotation of the arbor-holder relative to the saw cup is limited by contact of a longitudinal edge of a locking tab with an intersection between a curved and flat edge wall of the saw cup aperture. With this arrangement, the saw cup is locked axially and rotationally to the arbor-holder.
The inner cylindrical body of the arbor-holder according to the present invention has through its thickness dimension an axially disposed bore coaxial with the arbor-holder collar. The bore has internal left-hand threads adapted to receive an arbor which may be threaded into the bore through a front opening thereto in the front or outer face of the nose piece, either before or after the arbor-holder has been snap-locked into a saw cup as described above.
The arbor is provided with a shank which protrudes rearwardly from the rear surface of the arbor-holder and which is clamped in the collet of a power drill. A collet flange at the front end of the arbor-holder holds a pilot drill, and the rear face of the collet flange seats against the front face of the arbor-holder nose piece, when the arbor is threadingly tightened in the arbor-holder bore in a counterclockwise sense, as viewed from the front of the pilot drill. The rearwardly protruding shank of the arbor is then clamped in the chuck of a power drill, which is then powered on to rotate the hole saw in a clockwise sense as viewed from the shank end of the hole saw, and cut a circular hole through a workpiece, leaving a cylindrically-shaped plug of workpiece material lodged within the hole saw cup. The drill is then angled slightly away from an orientation perpendicular to the workpiece used to bore the hole, thus slightly cocking the hole saw cup within the hole cut through the workpiece, and thereby frictionally lodging the hole saw cup within the workpiece hole. The power drill is then powered on in a reverse sense to rotate the arbor in a reverse sense, thus causing the arbor and flange to be threadingly advanced within the arbor-holder bore, thereby ejecting the workpiece plug forwardly out from the saw cup body.
When it is desired to remove the arbor-holder from a saw cup body, e.g., to install the arbor-holder and arbor in a different saw cup body, which may be of a different size, the collar of the arbor-holder is pulled rearwardly from the front nose piece and saw cup body, thus retracting the locking tabs from the space between the flat sides of the nose piece and the adjacent curved peripheral walls of the saw cup aperture. With the locking tabs thus disengaged from the hole saw cup, the arbor-holder can be rotated counterclockwise to align the flats and curves of the nose piece once again with the correspondingly shaped edge walls of the saw cup aperture, thus allowing the nose piece and entire arbor-holder to be pulled rearwardly and disengaged from the saw cup body.